solr 中的group使用说明
参数说明
参数名 | 参数值 | 说明 |
group | true/false | if true, turn on result grouping（如果为true,结果分组） |
group.field | [fieldname] | Group based on the unique values of a field. The field must currently be single-valued and must be either indexed, or be another field type that has a value source and works in a function query - such as ExternalFileField. Note: for Solr 3.x versions the field must by a string like field such as StrField or TextField, otherwise a http status 400 is returned. （分组基于值域(field)唯一值来实现。该字段必须是单值的，必须是索引的。或者是另一种值域：有值源，而且工作在函数查询下，比如说扩展值域。注意：solr 3.x版本，值域的类型必须为string类型，比如StrField or TextField） |
group.func | [function query] | Group based on the unique values of a function query. (分组基于函数查询的唯一值。solr4.0以后才支持) |
group.query | [query] | Return a single group of documents that also match the given query. (返回一个匹配搜索的单个文档组，) |
rows | [number] | The number of groups to return. Defaults to 10. 返回的群组个数，默认是10 |
start | [number] | The offset into the list of groups. （该群列表中的偏移量） |
group.limit | [number] | The number of results (documents) to return for each group. Defaults to 1. (每个群组返回的结果数，默认是1) |
group.offset | [number] | The offset into the document list of each group. （每个群组的偏移量） |
sort | [sortspec] | How to sort the groups relative to each other. For example, sort=popularity desc will cause the groups to be sorted according to the highest popularity doc in each group. Defaults to "score desc". （怎么对群组排序，例如：sort=popularity desc会使群组按照 popularity的值降序排序，默认是"score desc"） |
group.sort | [sortspec] | How to sort documents within a single group. Defaults to the same value as the sort parameter. (单个群组内怎样排序，默认是和sort参数一样) |
group.format | grouped/simple | if simple, the grouped documents are presented in a single flat list. The start and rows parameters refer to numbers of documents instead of numbers of groups. (如果值是simple，分组后的文档记录是单一的平面列表。 start and rows指的是文档记录的数量，而不是群组的数量) |
group.main | true/false | If true, the result of the last field grouping command is used as the main result list in the response, using group.format=simple （如果为true,最后一个值域的分组命令的结果，被作为主要的结果列表，需要 group.format=simple）（不懂） |
group.ngroups | true/false | If true, includes the number of groups that have matched the query. Default is false. （如果为true,包括匹配查询的分组数。默认是false.警告，如果是在一个分布式环境里，这个参数设置为true,所有的文件，属于同一组必须位于相同的分片,否则计数将不正确。如果你使用SolrCloud，考虑自定义"custom hashing"） |
group.truncate | true/false | If true, facet counts are based on the most relevant document of each group matching the query. Same applies for StatsComponent. Default is false. (如果值为true,facet 总数是基于每组最相关的记录，和StatsComponent功能一样，默认是false) |
group.facet | true/false | Whether to compute grouped facets for the field facets specified in facet.field parameters. Grouped facets are computed based on the first specified group. Just like normal field faceting, fields shouldn't be tokenized (otherwise counts are computed for each token). Grouped faceting supports single and multivalued fields. Default is false. |
group.cache.percent | [0-100] | If > 0 enables grouping cache. Grouping is executed actual two searches. This option caches the second search. A value of 0 disables grouping caching. Default is 0. Tests have shown that this cache only improves search time with boolean queries, wildcard queries and fuzzy queries. For simple queries like a term query or a match all query this cache has a negative impact on performance |
